Pressure tank cars (e.g. DOT 112, 114 & 105 spec) are used extensively for the transportation of materials in the liquid or gaseous form, including hazardous materials. When the material is in the liquid or gaseous state, such tank cars are equipped with various safety devices to prevent leakage of such material during loading and unloading operations and to prevent leakage when the tank car is damaged or displaced from its normal position, especially when it is overturned. For a damaged or displaced tank car the problem is how to remove the enclosed material so that it can be transferred to other storage and transportation means should that be necessary. If the tank car is only slightly damaged or displaced from its normal position, such removal can usually be achieved by using the normal valved outlets on the tank car. However, if the normal valved outlets have been damaged or are inaccessible or the tank car has been overturned it is necessary to use other means to remove the material. Tank cars are equipped with usually two liquid valves for loading and unloading, one vapor valve and one safety valve at the loading dome -- the two liquid valves are attached to respective eduction lines that reach almost to the bottom of the tank car so that loading and unloading is of the liquid phase. The vapor valve is equipped with a short line so that the end of the line is in the vapor space. When a tank car is overturned the liquid valves cannot be used to remove the contents because the inlet to the line would be in the vapor phase. Hence it is necessary to use the vapor valve. Both the liquid and vapor valves are equipped with excess flow check valves which are closed by either the force of gravity or the flow of fluid at a rate higher than a pre-established value. Thus the removal of liquid through either vapor or liquid valve may be prevented by the excess flow check valve. High pressure inert gas could be applied to the vapor valve of an overturned tank car to displace the excess flow check valve back into the open position to allow the material to be removed through the vapor valve but this frequently fails to work because the subsequent flow of the material through the excess flow check valve causes it to close again, thus stopping the flow of the material. The Applicants are not aware of any prior art directed to overcoming this problem.